fix(pr): refuse pr comment and pr attachment on issues

Gitea serves pull request comments and attachments through issue
endpoints, so tea pr comment create 1 posted on issue #1. pr comment and
pr attachment commands now check that the number is a pull request, and
comment IDs that the comment is on one, and point at the issue command
otherwise: "#1 in alice/project is an issue, not a pull request; use tea
issue comment create 1". Issues gain a kind field (issue or pull) in JSON.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/pulls.go

@@ -34,7 +34,7 @@ $ tea pr merge --squash --delete-branch`
 	group.AddCommand(a.pullListCommand(), a.pullViewCommand())
 	a.addPullMutations(group)
 	group.AddCommand(a.pullEditCommand(), a.pullReadyCommand())
-	group.AddCommand(a.issueAttachmentCommand(), a.commentCommand())
+	group.AddCommand(a.issueAttachmentCommand(pullRef), a.commentCommand(pullRef))
 	return group
 }